Anti-islanding method and apparatus for distributed power generation
AssigneePlug Power Inc.
InventorRobert H. Wills
Life of this patent
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Abstract
The invention in the simplest form is a method and apparatus for reliably protecting against island situations with one or multiple power sources connected to an electric distribution grid. The method and apparatus detects variations in the voltage and frequency of the grid. An observed change in grid voltage causes a change in output power that is sufficient to cause an even larger change in grid voltage when the utility AC power source is disconnected. An observed change in grid frequency causes a change in phase or reactive output power that is sufficient to cause an even larger change in grid frequency. If several shifts in voltage or frequency happen in the same direction, the response to the change is increased in an accelerating manner.
Claims20
An anti-islanding apparatus for isolating a power source from a failed electrical grid, comprising
- a power converter connectable between said power source and said grid;
- a means for measuring a voltage of said grid;
- a means for calculating a voltage trend in said grid voltage, using a present grid
- voltage measurement and a prior grid voltage measurement;
- a means for calculating a positive feedback power converter control signal based on said voltage trend;
- a control circuit connected to said power converter, wherein said control circuit
- applies said control signal to said power converter;
- and
- a means of disconnecting said power source from said grid when said present grid
- voltage is outside pre-defined limits.
An anti-islanding apparatus for isolating a power source from a failed electrical grid, comprising:
- a power converter connectable between said power source and said grid;
- a means for measuring a frequency of said grid;
- a means for calculating a frequency trend in said grid frequency using a present
- grid frequency measurements and a prior grid frequency measurement;
- a means for calculating a positive feedback power converter control signal based on said frequency trend;
- a control circuit connected to said power converter, wherein said control circuit applies said control signal to said power converter;
- and
- a means of disconnecting said apparatus from said grid when said present grid frequency is outside pre-defined limits.
A method of preventing islanding of a power source on a distributed grid comprising the steps:
- measuring grid voltage;
- calculating a voltage trend in said grid voltage, using a present grid voltage measurement and a prior grid voltage measurement;
- calculating a power converter control signal in a same direction as said voltage trend;
- applying said power converter control signal to said power converter;
- and
- disconnecting said power source when said present grid voltage measurement is outside acceptable limits.
A method of preventing islanding of a power source on a distributed grid comprising the steps:
- measuring grid frequency;
- calculating a frequency trend in said grid frequency, using a present grid frequency
- measurement and a prior grid frequency measurement;
- calculating a power converter control signal in a same direction as said frequency trend;
- applying said control signal to said power converter;
- and
- disconnecting said power source when said present grid frequency measurement is outside acceptable limits.
Dependencies are inferred from the claim text.